image-size/dist/types/jxl-stream.cjs

get dimensions of any image file

'use strict';

// lib/utils/bit-reader.ts
var BitReader = class {
  constructor(input, endianness) {
    this.input = input;
    this.endianness = endianness;
    // Skip the first 16 bits (2 bytes) of signature
    this.byteOffset = 2;
    this.bitOffset = 0;
  }
  /** Reads a specified number of bits, and move the offset */
  getBits(length = 1) {
    let result = 0;
    let bitsRead = 0;
    while (bitsRead < length) {
      if (this.byteOffset >= this.input.length) {
        throw new Error("Reached end of input");
      }
      const currentByte = this.input[this.byteOffset];
      const bitsLeft = 8 - this.bitOffset;
      const bitsToRead = Math.min(length - bitsRead, bitsLeft);
      if (this.endianness === "little-endian") {
        const mask = (1 << bitsToRead) - 1;
        const bits = currentByte >> this.bitOffset & mask;
        result |= bits << bitsRead;
      } else {
        const mask = (1 << bitsToRead) - 1 << 8 - this.bitOffset - bitsToRead;
        const bits = (currentByte & mask) >> 8 - this.bitOffset - bitsToRead;
        result = result << bitsToRead | bits;
      }
      bitsRead += bitsToRead;
      this.bitOffset += bitsToRead;
      if (this.bitOffset === 8) {
        this.byteOffset++;
        this.bitOffset = 0;
      }
    }
    return result;
  }
};

// lib/types/utils.ts
new TextDecoder();
var toHexString = (input, start = 0, end = input.length) => input.slice(start, end).reduce((memo, i) => memo + `0${i.toString(16)}`.slice(-2), "");

// lib/types/jxl-stream.ts
function calculateImageDimension(reader, isSmallImage) {
  if (isSmallImage) {
    return 8 * (1 + reader.getBits(5));
  }
  const sizeClass = reader.getBits(2);
  const extraBits = [9, 13, 18, 30][sizeClass];
  return 1 + reader.getBits(extraBits);
}
function calculateImageWidth(reader, isSmallImage, widthMode, height) {
  if (isSmallImage && widthMode === 0) {
    return 8 * (1 + reader.getBits(5));
  }
  if (widthMode === 0) {
    return calculateImageDimension(reader, false);
  }
  const aspectRatios = [1, 1.2, 4 / 3, 1.5, 16 / 9, 5 / 4, 2];
  return Math.floor(height * aspectRatios[widthMode - 1]);
}
var JXLStream = {
  validate: (input) => {
    return toHexString(input, 0, 2) === "ff0a";
  },
  calculate(input) {
    const reader = new BitReader(input, "little-endian");
    const isSmallImage = reader.getBits(1) === 1;
    const height = calculateImageDimension(reader, isSmallImage);
    const widthMode = reader.getBits(3);
    const width = calculateImageWidth(reader, isSmallImage, widthMode, height);
    return { width, height };
  }
};

exports.JXLStream = JXLStream;